diff --git a/docs/fsharp/language-reference/type-extensions.md b/docs/fsharp/language-reference/type-extensions.md
index e5764f33d444b..ec0c2bff3b9a6 100644
--- a/docs/fsharp/language-reference/type-extensions.md
+++ b/docs/fsharp/language-reference/type-extensions.md
@@ -70,7 +70,9 @@ static member Method<T>(this T input, T other)
 This approach is particularly useful when the generic type parameter is constrained. Further, you can now declare extension members like this in F# code and define an additional, semantically rich set of extension methods. In F#, you usually define extension members as the following example shows:
 
 ```fsharp
-type seq<’T> with
+open System.Collections.Generic
+
+type IEnumerable<'T> with
     /// Repeat each element of the sequence n times
     member xs.RepeatElements(n: int) =
         seq { for x in xs do for i in 1 .. n do yield x }
@@ -84,7 +86,7 @@ Consider the following declaration:
 [<Extension>]
 type ExtraCSharpStyleExtensionMethodsInFSharp () =
     [<Extension>]
-    static member inline Sum(xs: seq<’T>) = Seq.sum xs
+    static member inline Sum(xs: IEnumerable<'T>) = Seq.sum xs
 ```
 
 By using this declaration, you can write code that resembles the following sample.
@@ -102,4 +104,4 @@ In this code, the same generic arithmetic code is applied to lists of two types
 ## See Also
 [F# Language Reference](index.md)
 
-[Members](members/index.md)
\ No newline at end of file
+[Members](members/index.md)